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First and Second Messenger Role of Calcium: Survival versus Apoptosis in Serum‐Free Cultured Granulosa Explants
Author(s) -
MUSSCHE SYLVIE,
LEYBAERT LUC,
D'HERDE KATHARINA
Publication year - 2000
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.2000.tb05603.x
Subject(s) - apoptosis , extracellular , calcium , fura 2 , homeostasis , chemistry , medicine , intracellular , endocrinology , programmed cell death , annexin , calcium in biology , channel blocker , bapta , biophysics , microbiology and biotechnology , biology , biochemistry , cytosol , enzyme
A bstract : In order to elucidate the causal relationship between increased intracellular free calcium ([Ca 2+ ] i ) and induction of apoptosis, serum‐free cultured granulosa cell (GC) explants were subjected to various experimental protocols interfering with normal Ca 2+ homeostasis. Modulation of apoptotic indices was calculated on DAPI‐stained GC explants. In some experiments [Ca 2+ ] i was measured with the Ca 2+ probe fura‐2 in combination with epifluorescence microscopy. Buffering of [Ca 2+ ] i with BAPTA‐AM resulted in inhibition of apoptosis, while increasing extracellular Ca 2+ (otherwise called [Ca 2+ ] e load) resulted in a biphasic response characterized by an initial inhibitory effect on apoptosis followed by a delayed phase of increased apoptosis that became apparent at 4 h after withdrawal of the [Ca 2+ ] e load. The initial inhibitory effect of the [Ca 2+ ] e load on apoptosis was dependent on the concentration of the load (range 2–50 mM), was augmented when the [Ca 2+ ] e load was applied in the presence of the Ca 2+ channel blocker methoxyverapamil, and was mimicked by applying Mg 2+ and Gd 3+ , two Ca 2+ ‐receptor agonists. These observations point towards the involvement of an extracellular Ca 2+ ‐sensing receptor (CaR). Measurements of [Ca 2+ ] i showed that the ion was increased just after [Ca 2+ ] e load, followed by recovery that was complete at 2 h after the load. Collectively these data suggest that a [Ca 2+ ] e load initiates apoptosis, becoming manifest 4 h later, by the provoked [Ca 2+ ] i increase, and this effect is preceded by an apoptosis‐inhibiting phase presumably involving CaR activation. We conclude that Ca 2+ may act as a first (extracellular) messenger promoting cell survival and as a second (intracellular) messenger activating the cell death pathway.